As shown in FIG. 1, a wireless communication system 10 comprises elements such as client terminal or mobile station 12 and base stations 14. Other network devices which may be employed, such as a mobile switching center, are not shown. In some wireless communication systems there may be only one base station and many client terminals while in some other communication systems such as cellular wireless communication systems there are multiple base stations and a large number of client terminals communicating with each base station.
As illustrated, the communication path from the base station (BS) to the client terminal direction is referred to herein as the downlink (DL) and the communication path from the client terminal to the base station direction is referred to herein as the uplink (UL). In some wireless communication systems the client terminal or mobile station (MS) communicates with the BS in both DL and UL directions. For instance, this is the case in cellular telephone systems. In other wireless communication systems the client terminal communicates with the base stations in only one direction, usually the DL. This may occur in applications such as paging.
The base station to which the client terminal is communicating with is referred as the serving base station. In some wireless communication systems the serving base station is normally referred as the serving cell. The terms base station and a cell may be used interchangeably herein. In general, the cells that are in the vicinity of the serving cell are called neighbor cells. Similarly, in some wireless communication systems a neighbor base station is normally referred as a neighbor cell.
The 3GPP LTE wireless communication system air interface is organized into radio frames, subframes, and Orthogonal Frequency Division Multiplexing (OFDM) symbols as shown in FIG. 2. Each radio frame comprises ten subframes numbered from subframe 0 to subframe 9. The radio frame duration is 10 ms and the subframe duration is 1 ms. In 3GPP LTE wireless communication system, a BS is referred to as evolved NodeB (eNB).
As per 3GPP LTE wireless communication system specifications, each cell broadcasts the access information about the system which is required for the client terminals to receive service. The system information is organized into the MasterInformationBlock (MIB) and a number of SystemInformationBlocks (SIBs). The MIB includes a limited number of essential parameters that are required to acquire other system information from a cell.
As per 3GPP LTE wireless communication system specifications, the MIB is transmitted on the Physical Broadcast Channel (PBCH) in subframe 0 as shown in FIG. 2. The MIB uses a fixed schedule with a periodicity of 40 ms and repetitions made within 40 ms. The first transmission of the MIB is scheduled in subframe #0 of radio frames for which the System Frame Number (SFN) mod 4=0, and repetitions are scheduled in subframe #0 of all other radio frames within the 40 ms window. An example of this is shown in FIG. 3.
As per 3GPP LTE wireless communication system specifications, the SIB1 is transmitted on a fixed schedule over the Physical Downlink Shared Channel (PDSCH) with a periodicity of 80 ms and repetitions made within each 80 ms window. The first transmission of SIB1 may be scheduled in subframe #5 of radio frames for which the SFN mod 8=0, and repetitions are scheduled in subframe #5 of all other radio frames for which SFN mod 2=0. An example of this is shown in FIG. 4.
As per 3GPP LTE wireless communication system specifications, the SIBs other than SIB1 are transmitted in SystemInformation (SI) messages and mapping of SIBs to SI messages is flexibly configurable by the Information Element (IE) SchedulingInformation included in the SIB1. Each SIB must be contained only in a single SI message. Only SIBs having the same scheduling requirement (periodicity) can be mapped to the same SI message. The SIB2 is always mapped to the SI message that corresponds to the first entry in the list of SI messages in SchedulingInformation. There may be multiple SI messages transmitted with the same periodicity. SIB1 and all SI messages are transmitted on PDSCH. An example of the mapping of SIBs to SI messages is shown in FIG. 5.
As per 3GPP LTE wireless communication system specifications, the SI messages are transmitted within periodically occurring time window, referred to as SI-window, using dynamic scheduling. Each SI message is associated with an SI-window and the SI-window of different SI messages do not overlap, i.e., within one SI-window only the corresponding SI is transmitted. The length of the SI-window is common for all SI messages, and is configurable. Within the SI-window, the corresponding SI message may be transmitted a number of times in any subframe other than Multicast-Broadcast Single Frequency Network (MBSFN) subframes, uplink subframes in TDD (Time Division Duplex), and subframe #5 of radio frames for which SFN mod 2=0. The client terminal acquires the detailed time-domain scheduling from decoding SIB1 which configures the SI-window length and the transmission periodicity for the SI messages. An example of the mapping of the SI messages to SI-windows is shown in FIG. 6. Each rectangular box in FIG. 6 represents one subframe. The shaded boxes are used to indicate the subframes that are used for scheduling SI messages within an SI-window. In the remainder of the present document the terms SIB2 and SI2 are used interchangeably. Decoding of SI2 provides SIB2 and possibly other SIBs depending on the mapping of other SIBs to SI2. SIB2 is always mapped to SI2.
As per 3GPP LTE wireless communication system specifications, the SI messages may be transmitted in the SI-window using dynamic scheduling by the eNB. The SI messages may be transmitted in all subframes in SI-window or the SI messages may be transmitted in some subframes in the SI-window. The eNB may have different SI message transmission scheduling in each SI-window for different SI messages.
Conventional methods depend on successfully decoding the SIB1 first to acquire the detailed time-domain scheduling and other information for other SI messages.